Martin Rees

Philosophers have debated the nature of "nothing" for thousands of years, but what has modern science got to say about it?

UK's Astronomer Royal Martin Rees shares his memories of the late star physicist Stephen Hawking.

Had the momentum of the 1960s been maintained over the next 40 years, there would be footprints on Mars by now. But after Apollo, the political impetus for manned spaceflight was lost.